Accompanied by: CD-Rom inserted into pocket of book.

Dr. Laj Ahuja is a retired soil scientist at USDA in Fort Collins, CO.

Dr. Liwang Ma is a research soil scientist at the USDA-ARS Rangeland Resources and Systems Research Unit at Fort Collins. Dr. Ma's research interests include the use of system ecological and biophysical models to quantify agricultural production and environmental impacts at multiple spatiotemporal scales in rangelands and croplands.